Full disclosure upfront: I am an early Kickstarter backer for Pebble. I do try an not let that make me biased in this comment.
My requirements in a smart watch are the following:
-Fully customizable watchface which can be displayed at all times (it's a watch; I shouldn't need to do anything just to see the time)
-Battery must last more than a couple of days. The longer the better. A whole week is a good start.
-It must be able to be fully submersible in water so I may shower and swim without any care
-The band must either be made of a durable fabric that is easily cleaned such as nylon or user replaceable in available sizes (skin condition)
-It needs to be able to provide useful alerts with contextual text to alleviate the need to pull my phone out of my pocket or run to it's location
-Further interactive functionality with my phone is a bonus
Why I prefer the Pebble:
The Pebble is by no means the perfect smartwatch. It even has a manufacturing flaw that I doubt will ever be addressed (rainbowin display in the sunlight). That being said, it ticks all of the above boxes. My phone is either in my pocket, near by, or on the charger up stairs. When ever I get a text message, phone call (Caller ID with the option to send to voicemail), e-mail, IM, meeting notification, reminder, or any other alert of my choosing, it displays on my watch. Through a 3rd party app, I can choose what app alerts to send to my watch. If I get too many alerts from an app, I can just have it not send to my watch. In many cases I get an alert that I just need to read and not respond to. When I'm on-call for work, I can see who's calling and whether it's worth running up stairs to my phone or getting out of bed to answer. I can also change music tracks or stations from my watch and they don't need to directly support Pebble either. In the car, I can change without taking my eyes off the road. Doing the dishes, I can change without getting my phone wet or it be near the sink.
The fact that an application doesn't need to natively support Pebble is a big plus. Any smartwatch needs to have an accompanying SDK and should leverage the existing APIs from the phone's OS to be able to integrate. Another cool thing I've got working is my phone security goes from a simple swipe to PIN requirement to unlock whenever my watch is out of range or the BT turned off; if someone happens to pick up my phone and walk off, it will lock with the PIN regardless if the screen is on and they're using it. Lastly a cool feature I should mention is I just need to flick my wrist in order for the backlight to come on so I can see what it says in the dark or use as a low light short range brief flashlight (I do this about once a week).
I have looked at the other smartwatches out there (here's a good list) and all of them had something missing or a poor attempt from my required list. Features like being able to take voice memos, use it as a headset or speakerphone, take pictures, and have a full color touch display are nice, but not one of my requirements. I'd wager the simplicity of physical buttons is better on a smartwatch than a touchscreen since one doesn't need to look at it to execute a command; a couple of examples would be glancing at an incoming call and dismiss it or changing tracks without looking.
I think the Galaxy Gear is a cute initial attempt from Samsung, but they have more work to do. Only getting text messages on the watch is silly. I don't need to be told I have a new e-mail since my phone already did that; let me see at least a snipet of the e-mail to determine if it's worth my time. I'd say Samsung has more work to do to open it up to other apps and phones not built by Samsung within the past year.